The Impact of BiLevel Positive Airway Pressure (BiPAP) Application Timing on Emergency Room Length of Stay in Patients With Pulmonary Edema: A Single-Center, Retrospective Cohort Study

Background: Bilevel positive airway pressure (BiPAP) is a form of non-invasive ventilation (NIV) that is used to help and facilitate breathing. Our objective is to evaluate the impact of BiPAP application time on the length of emergency room (ER) stay in pulmonary edema patients. Method: This is a retrospective cohort study that included patients who presented to the ER at King Abdullah Medical City (KAMC) from June 2019 to June 2021. The eligibility criteria for BiPAP application were congestive heart failure (CHF) and type 1 and type 2 respiratory failure, The data were collected from the Track Care system. We defined early BiPAP as BiPAP application time within one hour from admission, and late BiPAP more than one hour and we calculated the percentage of discharge within four hours in each group. Result: Out of 147 fulfilling study eligibility, 64% had CHF, 23% had type 2 respiratory failure and 13% had type 1 respiratory failure. For patients discharged within four hours, 85% were in the early BiPAP and 15% were in the late BiPAP groups (p = 0.001 as compared to the late discharge group). Discharge within four hours was observed with the following percentages in the study subgroups: CHF early BiPAP (84%), late BiPAP (16%) (p = 0.004), type 1 respiratory failure early BiPAP (79%), late BiPAP (21%) (p = 0.71) and type 2 respiratory failure early BiPAP (94%), late BiPAP (6%) (p = 0.89). Conclusion: Our results show that there is a significant outcome in early BiPAP application in decreasing the length of ER stay only in patients with pulmonary edema.


Introduction
Bilevel-positive airway pressure (BiPAP) is a form of non-invasive ventilation (NIV) that is used to help and facilitate breathing [1,2]. It is a method that supports inspiration and helps decrease respiratory work. The pressure is higher during inspiration and lowers during expiration [3]. BiPAP uses to treat acute respiratory failure (ARF) and showed a significant reduction in mortality rate, decreasing endotracheal intubation, and length of stay compared with other type of therapies [4]. It is a less invasive alternative to endotracheal intubation for treating congestive heart failure (CHF). It has been found to improve oxygenation, and hemodynamic stability, and reduce the need for intubation in the treatment of CHF [5]. BiPAP has also been shown to improve respiration and vital signs in acute pulmonary edema patients faster than CPAP [6]. There are some advantages of BiPAP over endotracheal intubation such as speech, swallowing, avoiding trauma to the trachea and larynx, and patient comfort [7].
The length of hospital stays, in general, will increasingly bear the cost on health care providers [1]. According to a study done in China, early use of BiPAP less than 48 hours in patients with acute respiratory distress syndrome (ARDS) in the intensive care unit (ICU) improved oxygenation and respiratory system compliance while also shortening the time spent on mechanical ventilation and in the ICU.
Consequently, no studies have ever demonstrated that early BiPAP application could reduce hospital stay, and the current literature providing evidence for the use of NIV for preventing post-extubation respiratory failure and reintubation is limited [3]. In addition, Non-Positive Pressure Ventilation (NPPV) has been shown to be effective when used as an initial mode of assisted ventilation. A meta-analysis study suggests that NIV is worth considering as a treatment option for patients with ARF [4][5][6][7]. However, another meta-analysis study does not support the use of NPPV in hypoxemic ARF and ARDS and is advised to be cautiously used in patients with ARDS [5].
To my knowledge, there are a few studies focused on the impact of BiPAP application time on the length of stay in pulmonary edema patients [8]. There is insufficient information and inadequate experience concerning NIV and a limited number of subjects participating in the studies [9]. In addition, there are limited studies that mainly focus on CHF and respiratory failure 1 and 2 as indications for BiPAP use [10]. Studies that related to our research were old and needed newly updated data [11]. Accordingly, this research aimed to evaluate the impact of early application of BiPAP in decreasing hospital length of staying in pulmonary edema patients.

Materials And Methods
The study designed as a retrospective cohort study and was carried out between August and October of 2021 on patients with pulmonary edema who were admitted via the emergency department at King Abdullah Medical City (KAMC), a tertiary center, which is located in Makkah city.
The inclusion criteria included any patient receiving BiPAP for type 1 and 2 respiratory failure and patients with CHF. The exclusion criteria were any subject underage of 18, respiratory failure due to nonpulmonary pathology, impaired consciousness, or any patient with a contraindication to bilevel positive air pressure (BiPAP).
We used a convenience sampling technique with an estimated sample size to be 36.45. the data were collected from the Track Care system of the KAMC hospital database, the data collection process took place between June 2019 to June 2021. The study included 237 and excluded 163 of the participants with a total number of 400 patients.
Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) Version 26. A descriptive analysis of the data was performed. Numerical variables are presented as arithmetic median and interquartile range since they had abnormal distribution. Categorical data are presented as absolute numbers, and category frequency is expressed as percentages. The t-test was used to compare the groups. The level of significance was set at p < 0.05 or 5% to find a possible association between certain factors and the length of stay among the admitted patients.
The proposal of this study had been revised and approved by the ethics committee of King Abdullah Medical City (KAMC) with IRB number 21-812.

Discussion
Most of the participants in the present study are from elder populations, with 65% being over 70 years old and, 89% being older than 51 years. This may reflect years of exposure to numerous risk factors, some of which could involve smoking, pollution, obesity, chronic diseases like hypertension or diabetes mellitus, or infections that may significantly impact heart and lung productivity, leading to more vulnerable status. In the present study, the majority had a high body mass index (BMI), thus provoking a greater need for ventilation modalities. A relevant article found that those with a high or morbid BMI had better outcomes compared to those with a normal BMI [12]. Of most participants, 92.50% were diagnosed with dyspnea related to CHF, with a lesser occurrence of both type 1 and 2 respiratory failures. Concerning the direct impact of BiPAP application, both heart rate and respiratory rate improved at the time of BiPAP application. Some reverse effects were documented on the oxygen partial saturation.
In CHF, early application of BiPAP reduced the length of emergency department stay (p < 0.05), which is consistent with a recent encounter in a study that reported NIV to be very effective in the reduction of intubation need along with overall mortality among CHF patients [13], and this might due the nature of the pathology as in heart failure the lung is intact but impacted by the congestion of the heart and the flow, whereas in respiratory failure the lung is primarily affected. A 2016 meta-analysis reported no significant association between noninvasive positive pressure ventilation (NPPV) among admitted patients or the length of an intensive care unit (ICU) or hospital stay. Gender and BMI did not impact the length of hospital stay, as many elderly patients may have similar disease courses over the years, but this is a recommendation and a gap for further research (Table 4) [14,15].

Reason for BiPAP applications P-value
Patient with type I respiratory failure due to primary pulmonary pathology. 0.077 Patient with type II respiratory failure due to primary pulmonary pathology. 0.035 Patient with congested heart failure 0.001

TABLE 4: Chi-square tests showing the p-value and the significant p-value
It is shown the significance in connecting early BiPAP with early discharge (p < 0.05).
As 116 (49.2%) of the total 236 patients were on early BiPAP, whereas the remaining 120 (50.8%) used BiPAP after an hour, this divided the sample into nearly two equal groups, which gives a more accurate assumption about the results. Generally, the BiPAP application time does not show significance regarding the discharge time. After classifying the patient according to the reason for BiPAP application, no significant found association between BiPAP application time and discharge time among types 1 and 2 respiratory failure patients. A meta-analysis performed on the NIV effect on acute respiratory failure supported our finding, which suggests that the usage of NPPV does not influence the length of hospital stay [16].
There was a significant change in the discharge time in patients with CHF, as 61 (46.9%) of the early BiPAP group were discharged within four hours, taking into consideration that cardiogenic pulmonary edema was the most common reason for BiPAP application in 153 (65%) of our sample. In contrast, other studies demonstrate either uncertainty about the effect of NPPV on the length of hospital stay [16] or that no difference was found [17] among CHF patients.
Among all participants, 158 out of 236 reached the target of SpO 2 (94%), 85 patients (53.8%) received BiPAP within the first hour, and 73 (46.2%) applied BIPAP after the first hour passed. There was a slight improvement for those who received it within the first hour of the presentation.
There is a significant association of BiPAP in patients with type 1 respiratory failure compared to type 2, the highest indication for BiPAP was CHF which resulted in noticeable outcomes with BiPAP administration and SpO 2 [18][19][20]. The largest body of evidence on the use of NIV comes from patients with chronic obstructive pulmonary disease (COPD) having exacerbation and respiratory failure [21][22][23]. NIV is effective in acute respiratory failure of various etiologies, therefore BiPAP effectively and safely provided early improvement and resolution of breath and SpO 2 [18].
The strength of this study is the first study in Saudi Arabia. One of the limitations encountered was the lack of data and that it was conducted only in one tertiary hospital, which had only complicated cases. Furthermore, more than half of the participants were from the elderly population.

Conclusions
Based on our findings, only patients with pulmonary edema due to CHF benefited from early BiPAP in shortening the duration of their hospital stay. The strength of this study is the first study in Saudi Arabia. Further research is encouraged to explore the efficacy of BiPAP administration in different settings and centers, along with possible associations between various etiologies or risk factors that may impact or stand as an obstacle to healthcare success and fruitful outcomes.

Additional Information Disclosures
Human subjects: Consent was obtained or waived by all participants in this study. King Abdullah Medical City issued approval 21-812. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.